In hydraulic systems it is often necessary to create a timing sequence so that different operations performed by the hydraulic system are done at prescribed intervals relative to one another. The prior art includes various methods for keying a movable piston to a timing mechanism so that, as the piston is moved to a particular position, a timer valve is actuated thereby sequencing further operation of a hydraulic system. A problem in prior art actuating systems has been the existence of fairly complex mechanisms having numerous components which decrease the reliability of the system.